1. Field of the Disclosure
Embodiments of the present disclosure generally relate to a magnetic read head sensor for use in a hard disk drive. The read head sensor is a magnetoresistive effect type. In particular, the embodiments relate to read head sensors utilizing dual capping layer in the sensors.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing and reading magnetic transitions corresponding to host data. The read and write heads are connected to a signal processing circuitry that operates according to a computer program to implement the writing and reading functions.
The read head of a hard disk drive includes a spin valve element utilizing a magnetoresistive effect. By sensing the relative magnetizations of two ferromagnetic thin films, such as a free magnetic layer and a pinned magnetic layer, sandwiching an intermediate layer, magnetic information can be read from nanoscale magnets on the disk. Reductions in various dimensions of the sensor element and improvements in the film characteristics have contributed to improvements in recording density, allowing current recording tracks to achieve a width less than approximately 100 nanometers. However, as the track width is narrowed, the effect of noise (mag-noise) generated by thermal vibrations during magnetization of the free magnetic layer on the head signal-to-noise ratio (SNR) become prohibitively large. Since the mag-noise increases proportionally as the playback output increases, the head SNR saturates at some maximum value. Thus, a reduction in the mag-noise has become increasingly important. Magnetic biasing (domain control) of the free magnetic layer as well as the control for low magnetic coupling is effective in reducing mag-noise.
Therefore, there is a need in the art for a sensor structure that may minimize mag-noise with low magnetic coupling in the sensor structure.